Cracking in concrete
Now let's think about cracking in dams -- this is called
Cracking Dams, right? Let's look at
concrete dams specifically.
First, what is concrete?
concrete = rocks + special dirt + water |
| The special dirt is called cement. But you
can't dig it up in back yards -- you have to buy it in bags.
It acts like glue for the rocks when mixed with water.
When it gets hard
it gives off heat because a chemical reaction is happening. |
 |
(ref: F.F. Abraham et al) |
Once the concrete is hard, it cools down. If you have a
large amount of concrete, this can be a big change in temperature -- which can
cause cracks!
Watch this movie of a crack at a very small scale, like under a
microscope.
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|
As you saw earlier, concrete is good when you push on it. But
when you pull on it, that's when cracks grow. | |
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